Firefox engineers discover a Windows Defender bug that causes high CPU usage

Post by 0000000000100 » Wed, Apr 05, 2023, 8:33 PM UTC

stkdump wrote: post #34

boringuser2 wrote: post #21

Earlier quoted context omitted.

Firefox is significantly slower than chrome. This usually doesn't matter, but you can immediately see it in any page that A) has a massive DOM or B) uses complex regular expressions that eat up the engine

I've read that a number of times now, but I have trouble matching it to my perceptions. Can you point to a specific website where you notice that slowness and then describe what action is slower? (Initial load, clicking stuff, scrolling, etc.) Just as an example, loading jslinux.org for me in Firefox is about twice as fast than in Chrome. That might be a special case of course, because it is a very special type of wo…

Post by crooked-v » Wed, Apr 05, 2023, 8:36 PM UTC

cptskippy wrote: post #58

crooked-v wrote: post #51

Earlier quoted context omitted.

Put 10,000 or so event handlers with their own DOM updates on a page. Chrome will run it smoothly (taking up a huge amount of RAM in the process), Firefox won't.

What is the definition of huge amount of RAM? How does Chrome perform when it's RAM constricted? Are we blaming Firefox for poorly designed websites? It feels like this is a straw man constructed to bash Firefox, rather than a real world scenario.

Post by sfink » Wed, Apr 05, 2023, 8:41 PM UTC

Diggsey wrote: post #35

mconley wrote: post #4

TL;DR: Windows Defender had a bug that made certain system calls expensive on CPU cycles when Defender's Real-time Protection feature is enabled. After discovery, Mozilla reported this issue to Microsoft. Microsoft is releasing a patch that should result in lower CPU usage when using Firefox on sites like YouTube (a ~75% CPU usage reduction was noted when browsing YouTube in Firefox with the fixed version of Defender…

Well, also Firefox is making an excessive number of calls to that slow system call compared to other browsers (Chrome, Edge).

Post by zamadatix » Wed, Apr 05, 2023, 8:45 PM UTC

rascul wrote: post #53

marcodiego wrote: post #13

> a ~75% CPU usage reduction was noted when browsing YouTube in Firefox I wonder how many of the people who say "Firefox is significantly slower than chrome" are using windows... On my computer, Firefox IS slower than chrome but (with ad blockers enabled) by an insignificant amount. By still being "the last remaining mostly independent, maintained and reasonably popular browser" I'd prefer it to use over chrome even…

I just ran a test at https://browserbench.org/Speedometer2.1/ Firefox scored 89.5 ±1.7 Chromium scored 87.3 ±2.9 I guess that means Firefox did faster for those tests. I don't use Chrome or Chromium based browsers in general so I don't know how they compare in "feel". I am on Linux.

Post by zokier » Wed, Apr 05, 2023, 8:46 PM UTC

Cthulhu_ wrote: post #37

ivanmontillam wrote: post #25

I've experienced a bug related to the on-disk real-time scanning of Windows Defender, but instead with 100% disk bandwidth usage for unreasonable amounts of time. I purchased a license of a proper antivirus software to avoid that bug and the performance issues gone away. When you install another AV software, Windows Defender steps down and leaves scanning to the 3rd-party security solution. I selected one of the most…

> I purchased a license of a proper antivirus software Which is that? For years (and come to think of it, this goes back to the 2000's or even 90's), AV / antimalware software comes across as scareware, using tricks to ensure you're afraid of not having it. And second, who here has ever had a virus in the past ten years?